Speed doesn’t kill. Speed differences do, however. You are safest staying close to the median speed for that road, regardless of what the posted limit is.
Amen. I'm generally a left-lane driver, but I really do get annoyed by the people who zoom up behind me and tailgate when I'm maintaining a safe distance behind the car in front. When it's safe to do so, I'll get over to let the dude pass -- but meanwhile, riding my ass is not helpful.